Uncertainty of the astrophysical ~(17,18)O(α,n)~(20,21)Ne reaction rates and the applicability of the statistical model for nuclei with A < 20

摘要

Background: The (α,n), and (α,γ ) reactions on ~(17,18)O have significant impact on the neutron balance in the astrophysical s process. In this scenario stellar reaction rates are required for relatively low temperatures below T_9 < 1. Purpose: The uncertainties of the ~(17,18)O(α,n)~(20,21)Ne reactions are investigated. Statistical model calculations are performed to study the applicability of this model for relatively light nuclei in extension to a recent review for the 20 ≤ A ≤ 50 mass range. Method: The available experimental data for the ~(17,18)O(α,n)~(20,21)Ne reactions are compared with statistical model calculations. Additionally, the reverse ~(20)Ne(n,α)~(17)O reaction is investigated, and similar studies for the ~(17)Fmirror nucleus are provided. Results: It is found that, on average, the available experimental data for ~(17)O and ~(18)O are well described within the statistical model, resulting in reliable reaction rates above T_9 > 1.5 from these calculations. However, significant experimental uncertainties are identified for the ~(17)O(α,n_0)~(20)Ne (ground state) channel. Conclusions: The statistical model is able to predict astrophysical reaction rates for temperatures above 1 GK with uncertainties of less than a factor of two for the nuclei under study. An experimental discrepancy for the ~(17)O(α,n)~(20)Ne reaction needs to be resolved.